This invention pertains to the art of protective devices and more particularly to a thread protecting device.
The invention is particularly applicable to a thread protector for protecting the external threads of tubing or pipe and, more particularly, to the external threads on tubing, casing and drill pipe used in the natural gas and oil industry. However, it will be appreciated to those skilled in the art that the invention could be readily adapted for use in other environments as, for example, where similar protective devices are employed to protect other types of fragile or destructible threaded areas.
Conventional tubing and pipe threads are generally V-shaped in cross-section. Because of the handling and storage techniques generally employed with tubing and pipe, the threads are often exposed to harsh treatment during manufacture, shipment and use. This can cause particular damage to the crests of the threads by way of nicks, indentations and deformations resulting in their being unuseable. Furthermore, the tubing, casing and drill pipe to which the subject invention is particularly directed are frequently stored for prolonged periods of time in severe and corrosive environments such as wet, salty sea air and/or hot and sandy desert locations. If not properly insulated from such harmful environments, any threaded areas may quickly become unserviceable.
Various forms and types of thread protectors have heretofore been suggested and employed in the industry, all with varying degrees of success. It has been found that the defects present in most prior thread protecting devices are such that the devices themselves are of limited economic and practical value.
Typically, these prior thread protectors have variously comprised cup-shaped members formed from relatively heavy plastics, metals or metal-plastic combinations.
Prior heavy plastic protectors have suffered a number of inherent problems. It has been found that prolonged storage or exposure to harsh weather will cause many such devices to become out-of-round. This makes it difficult to properly mount or start them on the tubing, thereby creating consequent loss of time. In these instances, customers have been faced with incurring a small additional labor cost due to the extra time required in such protector mounting operations. In addition, protectors of all plastic construction have not withstood the impacts and blows received in handling. For example, due to their elasticity, many prior designs permit protector "rub off" from the tubing during the reciprocative back and forth shifting experienced during transportation in gondolas and trucks. Furthermore, the sharp blows received in loading and unloading may pierce or cut the plastic and, consequently, damage the underlying threads. However, where the protector side walls have been made thicker to withstand such blows, they are of excessive and unmanageable physical dimensions which substantially inhibit the efficient storage, handling and transportation of the tubing.
Prior protectors of all metal construction have generally comprised steel stampings or heavy wall tapped steel. Due to the sharp edges that result from the methods of manufacture used, workers handling them are more prone to injury by cuts or nicks. In addition, metal protectors will not cushion any impact or sharp blows to the tubing and may transfer them to the threads thereby causing thread damage. A further problem with all metal protectors is that they permit metal-to-metal contact. In the aforementioned harsh environments, this may be ruinous as the protector may rust to the tubing. This problem may be avoided by applying grease to the protector and tubing threads, but this requires additional labor costs as well as material expense.
Generally, prior protectors of metal-plastic combination construction have comprised metal casings on plastic sleeves. Typical of such constructions is the one shown in U.S. Pat. No. 3,000,402 to Bowman. These types of devices have had particular problems associated therewith as the metal shells or casings have a tendency to become disengaged from the associated plastic sleeve due to axial forces encountered during tubing handling and transporting. This separation is chiefly due to the substantial difference between the outside diameter of the protector and the outside diameter of the tubing which results in a jutting protrusion normal to the surface of the tubing that has been particularly susceptible to receiving axial forces. An additional problem resides in the fact that the metal shells or casings have generally been friction-fitted to an associated sleeve. The harsh environments to which the tubing and protectors are exposed have caused variances in the physical dimensions of the protector components which has resulted in additional susceptibility for disengagement or separation thereof.
The present invention contemplates a new and improved device which overcomes all of the above referred to problems and others to provide a new thread protector which is simple in design, economical to manufacture, readily adaptable to a plurality of uses with threaded members having a variety of dimensional characteristics, easy to install, easy to remove and which provides improved insulation from weather and handling hazards.